V A N D E R B I LT S T U D E N T
VOLUNTEERS FOR SCIENCE
FA L L 2 0 1 2
T R A I N I N G P R E S E N TAT I O N
I. INTRODUCTION
What are some properties of light?
 Light travels in straight lines.
 Show students the red laser.
A. Laser Light—to show students that light travels in a straight line.

Obtain the bottle of flour from the kit.

Shine the laser light towards a wall away from the students.

Compress bottle steadily and lightly so that the flour drops through the path of the laser light in a
constant stream.

Students should be able to see the laser light reflected upon the particles of flour.
Today’s lesson is going to focus on refraction.
Divide the class into 8 groups.
II. REFRACTION
Give each group of students a jar containing water
and a straw lying at an angle in the jar.
Tell students to rotate the jar while looking at the
straw and ask them what they observe.
Tell students to unscrew the lid and to hold the
straw vertically in the center of the jar so that it is
half in/out of the water.
Have them look at the straw through the side of
the jar and slowly move the straw to either side of
the jar (do not move the jar or your head).
Explain that the bending of light (refraction)
occurs when light waves pass from one medium to
another.
III. THE APPEARING COIN
Place the Styrofoam cup with the penny on the
desk.
Select one student in each group to pour the
water while the other students in the group
stand and observe the coin.
Tell them to stand in a position where they can
easily see the coin.
Now have the students slowly back up until the
coin has just disappeared from sight.
Tell the designated student to slowly pour water
into the cup.
Tell students to raise their hands as soon as
they can see the coin again.
III. THE APPEARING COIN (CONT.)
Explain that refraction causes this
effect.
When water is added, the light is
bent so that the coin becomes
visible (light travels through one
medium to another).
IV. DISAPPEARING CRYSTALS
Give each pair a water gel ball and a glass
marble (in a 1oz cup) and a jar of water.
Ask students to describe the water gel ball
and the marble.
Tell students to put the marble into the jar
of water.
Ask students if they can see the marble?
(yes)
Explain – refractive index of water and glass
are different so that the light waves are bent
when they enter the marble.
IV. DISAPPEARING CRYSTALS (CONT.)

Now put the water gel ball into the water.
Can you see it? (No)

Explain – these gel balls are made up
almost entirely of water (99%). So the
refractive index of water and the ball is
the same. It is difficult to see the spheres
in water because light rays are not bent
when they travel between two substances
with the same indices of refraction.

Ask students what they could do to make
the water gel ball appear visible?

What happens when you put a laser beam
thru the water plus water gel ball? (the
laser shows a path through the gel).

What happens when you put food coloring
into the water? Add a drop of blue food
coloring and show the students that you
can now see the water gel ball.
REVIEW
Review basic concepts with students and collect all materials
Make sure that all lasers have been returned